Stethacanthus is an extinct genus of shark which lived in the Early Carboniferous epoch, around 360 million years ago. Fossils have been found in Europe and North America.

Stethacanthus was around 70 centimetres (2.3 ft) long, and in many respects, had a typical shark-like appearance. However, it is best known for its unusually shaped dorsal fin, which resembled an anvil or ironing board. Small spikes (enlarged versions of the dermal denticles commonly covering shark skin) covered this crest, and the shark's head as well. The crest may have played a role in mating rituals, or used to frighten potential predators.